Prior-Art Non-Evacuated Two-Phase Heat-Transfer Systems
1. H.sub.2 O Systems
All, or almost all, prior-art non-evacuated two-phase heat-transfer systems employ H.sub.2 O as their heat-transfer fluid. I shall hereinafter refer to such systems as `non-evacuated two-phase heat-transfer H.sub.2 O systems`, or equivalently as `conventional heat-transfer systems`. In the latter term the word `conventional` signifies that air enters into the systems` one or more heat-transfer fluid circuits while the systems are inactive, namely while they are not transferring heat from a heat source to a heat sink.
Probably, the most frequently encountered conventional heat-transfer steam systems are those used for heating a building and its service or domestic water, or for supplying heat to an industrial process, with heat obtained from the combustion gas of a fossil fuel.
Perhaps the next most frequently encountered conventional heat-transfer steam systems are those used to recover waste heat with a waste-heat boiler and to transfer the recovered heat to a heat sink where it can be utilized.
Other current applications of conventional heat-transfer steam systems include solar heating applications in which the systems' evaporator is the feed of a concentrating solar collector.
Obsolete applications of conventional heat-transfer steam systems include systems for cooling vacuum tubes. Such systems are disclosed and claimed by Privett in U.S. Pat. No. 2,110,774.
Non-evacuated two-phase heat-transfer H.sub.2 O systems, or equivalently conventional heat-transfer steam systems, suffer from the well-known ills arising from the ingestion of air into their heat-transfer fluid circuits; and from the use of make-up water to replenish the heat-transfer fluid expelled with air from these circuits each time such systems are activated after they have been inactive for a long enough time interval for them to ingest a significant amount of air. The foregoing well-known ills are great enough for single phase heat-transfer systems, employing H.sub.2 O in its liquid phase as their heat-transfer fluid, to have displaced non-evacuated two-phase heat-transfer H.sub.2 O systems for many applications not requiring the former systems to operate at unacceptably-high pressures.
2. Non-H.sub.2 O Systems
Very few, if any, prior-art non-evacuated two-phase heat-transfer systems employ a fluid other than H.sub.2 O as their heat-transfer fluid. The reasons for this include the following three facts: